<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8">
        <title>Title</title>
    </head>
    <body>
        <div id="app" v-cloak>
            <h2 class="active">{{message}}</h2>
            <h2 class="title" :class="['active', 'line']">{{message}}</h2>
            <h2 class="title" :class="[active, line]">{{message}}</h2>
            <h2 class="title" :class="getClasses()">{{message}}</h2>
        </div>
        <script src="../../js/vue.js"></script>
        <script>
          const app = new Vue({
                el: '#app',
                data: {
                    message: '你好呀',
                    active: 'aaaaaa',
                    line: 'bbbbbb',
                },
                methods: {
                    getClasses: function () {
                        return [this.active, this.line]
                    }
                }
            }) 
        </script>
    </body>
</html>